So no movies or music in your brain only spikes representing (coding for) these movies and music. In our current understanding, sensory, motor, emotional, etc., information is represented by a particular set of neurons that “fire” these spikes. Synaptic inputs are the elementary (input) sources to neurons and, typically, many (excitatory) of them are required to summate (“temporal summation”) to generate a highly (“all or none”) output signal – the notorious spike (or “action potential”). In the present module we will proceed to deal with the active electrical aspects of neurons. In the previous module we learned that: 1-neurons are electrical devices, 2 - that the membrane behaves as an RC circuit, 3 - that synapses operate by opening a new cross-membrane conductance attached with a battery. In this module we are covering "Electrifying brains – active electrical spikes".
This module is more technical than the more descriptive first two lessons we encourage those of you who are not familiar with basic electricity (resistance, capacitance, Ohms law and Kirchoff’s law) to read about these in the sources links for this week’s lecture. Most interestingly, there are two types of synapses in the brain – “excitatory” and “inhibitory” – we will discuss how these two opposing signals interact in the receiving ``neuron. We will also show that when the synapse is activated, it generates an analog electrical signal (“the post-synaptic potential”, PSP) in the receiving (“post-synaptic”) cell. We will show that, at the quiescent state, the difference in electric potential across the cell’s membrane is always negative inside the cell (“the “resting potential”) we next show that the membrane behaves like an electrical (resistance-capacitance) RC circuit and highlight the notion of “membrane time constant” and, consequently, the ability of neurons to summate (in time) successive (synaptic) inputs (“electrical memory”) – a fundamental mechanism utilized by the brain. active) electrical properties of neurons. Here we will describe only the passive (vs. We will show that neurons are electrical device and learn what enables neurons to become “electrifying”. In this module we will discuss the "Electrifying brain – passive electrical signals".
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